First off... newbie alert. I may as well jump in though.
Most any of the suggestions so far will work fine. I've done it with recip.
saw, jig saw, and router (and dremel with a router bit). The router
requires a short piece of wood screwed to the router base and then the
other end tacked in at the center of the circle. Obviously it takes a few
passes and extra care on the final pass.
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